Deposition of osmotic absorbent onto a capillary substrate without deleterious interfiber penetration and absorbent structures produced thereby

Abstract

An absorbent structure comprising freestanding osmotic absorbent sites disposed on or within a capillary substrate. The sites extend outwardly normal to the plane of the absorbent structure or fill apertures within the plane of the absorbent structure. Upon imbibing liquids, the sites of osmotic absorbent can expand without constraint from the substrate.

What is claimed is: 
     
       1. An absorbent structure comprising: a generally planar fibrous capillary substrate; and   at least one site of an in situ polymerized osmotic absorbent hydrogel polymer having a proximal end joined to said fibrous capillary substrate, said osmotic absorbent hydrogel polymer further having a distal end freestanding from said capillary substrate, whereby said distal end can expand without constraint from said substrate upon imbibing liquids,   said fibrous capillary substrate comprising regions of two different densities, an essentially continuous network high density region and a plurality of discrete low density regions, wherein said sites of the osmotic absorbent hydrogel polymer are disposed on said low density regions.   
     
     
       2. An absorbent structure comprising: a generally planar fibrous capillary substrate defining an X-Y plane and a Z-direction orthogonal thereto; and   at least one site of an in situ polymerized freestanding osmotic absorbent hydrogel polymer joined to said fibrous capillary substrate and extending outwardly therefrom in the Z-direction whereby at least one said site of freestanding osmotic absorbent hydrogel polymer can expand in the X-Y plane without constraint from said substrate upon imbibing liquids,   said fibrous capillary substrate comprising regions of two different densities, an essentially continuous network high density region and a plurality of discrete low density regions, wherein said sites of the osmotic absorbent hydrogel polymer are disposed on said low density regions.   
     
     
       3. An absorbent structure according to claim 2 wherein said osmotic absorbent hydrogel polymer is distributed on said fibrous capillary substrate and joined thereto in a plurality of discrete sites and said fibrous capillary substrate comprises an essentially continuous network in which said sites are disposed. 
     
     
       4. An absorbent structure according to claim 2 wherein at least one said site of the freestanding osmotic absorbent hydrogel polymer is joined to said fibrous capillary substrate at a proximal end of said site of osmotic absorbent hydrogel polymer, and has interfiber penetration of said fibrous capillary substrate at said proximal end. 
     
     
       5. An absorbent structure according to claim 1 wherein at least one said site of the freestanding osmotic absorbent hydrogel polymer is joined to said fibrous capillary substrate at a proximal end, and has interfiber penetration of said fibrous capillary substrate at said proximal end. 
     
     
       6. An absorbent structure comprising a generally planar fibrous capillary substrate and at least one site of an osmotic absorbent hydrogel polymer joined thereto, said absorbent structure made by the process comprising the steps of: providing a generally planar fibrous capillary substrate;   providing a liquid precursor;   increasing the kinematic viscosity of said liquid precursor to at least 2,000 centipoise;   disposing said liquid precursor on said substrate in at least on discrete site; and   in situ polymerizing said liquid precursor to form at least one discrete site of an osmotic absorbent hydrogel polymer joined to said substrate at a proximal end of said discrete site of said osmotic absorbent hydrogel polymer and having a distal end freestanding from said substrate, whereby said distal end can expand without constraint from said substrate upon imbibing liquids.   
     
     
       7. An absorbent structure made according to the process of claim 6 wherein said step of increasing said kinematic viscosity comprises the step of adding a thickening agent to said liquid precursor. 
     
     
       8. An absorbent structure made according to the process of claim 6 wherein said step of increasing said kinematic viscosity comprises partially prepolymerizing said liquid precursor.